1. Field of the Invention
The invention relates to media element libraries for data storage.
2. Description of the Related Art
Magnetic tape cartridges, magnetic disks, and optical disks are all widely used as peripheral memory storage devices for computer systems. Large computer systems often operate in conjunction with external libraries of dozens of media elements as well as the media element readers used to record and retrieve the data. Although originally such media elements were selected and loaded manually, automated libraries were developed to expedite the handling of the media elements. These systems include robotics for accessing and retrieving media elements from storage locations, and loading the retrieved media element into an appropriate reader.
Some embodiments of such libraries comprise a small number of magnetic tape cartridges, six or ten being typical, and one or two tape drives housed in a single enclosure. Some systems have also been developed which comprise several smaller modules coupled together in a single rack. A system of this type is described in U.S. Pat. No. 5,870,245 to Kersey et al. The disclosure of U.S. Pat. No. 5,870,245 is hereby incorporated by reference in its entirety.
As data storage requirements for computer systems have increased, the volumetric efficiency of a library, that is, the number of media elements that can be stored per unit volume of the apparatus, has become an important factor in media library design. Maximizing volumetric efficiency requires careful consideration of the arrangement of media elements within the library, as well as the robotic system that retrieves and transports the media elements. Libraries that store media elements in a rotating circular carousel generally need a relatively small volume for media element transport robotics because the rotating carousel allows access to all of the media elements from one stationary position at any one point along the circumference of the carousel. However, the packing density of rectangular media elements such as tape cartridges is limited in a circular arrangement. One embodiment of a library with a carousel media element storage configuration is illustrated in U.S. Pat. No. 5,285,333 to Barr et al.
Alternatively, media elements may be stored as linear arrays of adjacent media elements. Storing media elements in linear arrays results in a high media element packing density, but requires more room for transport robotics because the transport robotics needs to travel up and down along the array to retrieve selected media elements. An example of this type of system is provided in the Kersey, et al. patent mentioned above. In addition, if more than one linear array is provided, more complex and expensive robotic transport robotics are needed to access all of them. It would therefore be beneficial to produce media element libraries with a high density of media elements as well as relatively simple and inexpensive robotic transport systems.
In one embodiment, the invention includes a robotic media handling system comprising first and second linear track segments, wherein one of the segments is pivotably mounted on an axis of rotation. A media element transfer carriage comprising a storage location for at least one media element is movably mounted to one of the track segments.